The present invention relates to loud speakers having a generally horizontal 360.degree. radiation pattern, and more particularly to loud speakers that can be vertically stacked for use as high powered sirens and the like.
High power loud speakers are known for use as sirens and horns to serve an alarm or warning function in environments such as navigation channels, fire stations, power plant perimeters, etc. Some of these loud speaker designs are also suitable for use in auditoriums or other large areas where communication to a large group of assembled persons is required. One type of known loud speaker arrangement for such use, has been commonly referred to as a "vertically stacked" siren or speaker system.
In one such arrangement, as disclosed in U.S. Pat. No. 3,153,783, a plurality of vertically stacked hyperbolic horns are arranged in spaced apart pods or envelopes, the space between the pods defining a sound director which disperses the sound horizontally in all directions. In the system disclosed in this patent, the profile of each envelope or pod completely surrounds the profile of an individual horn and associated driver.
Efforts have been made to increase the efficiency and/or reduce the cost of vertically stacked speaker arrangements. One example is disclosed in U.S. Pat. No. 2,820,525, in which a compound horn is oriented vertically upward from the bottom of the assembly and another compound horn is oriented vertically downward from the top of the assembly, each horn having associated with it a plurality of spaced apart pods. Sound transmitting channels from each portion of the horn lead to generally hyperbolic director surfaces between pods. Each channel has a different length based on the length of the portion of the horn to which it is connected, such that the total distance traveled by the sound wave from each portion of the composite horn, is substantially the same.
Although the examples of known loud speakers or siren systems identified above, and similar variations, are capable of producing high sound intensity, the need exists for improving the reliability, fabrication cost and operating efficiency involved in the manufacturer and use of this type of siren or loud speaker system.